Ink-jet ink compositions typically comprise a liquid vehicle and a colorant, the latter of which may be a dye or a pigment. Ink-jet inks used in photographic image printing almost always utilize water-soluble dyes. As a result, such dye-based ink-jet ink compositions are usually less waterfast than pigment-based ink-jet ink compositions, e.g., images tend to shift in hue and edge sharpness is reduced upon exposure to humid conditions. In addition, images created from these water-soluble dye-based ink-jet ink compositions tend to fade over time, such as when exposed to ambient light and/or air.
Print media surfaces can play a key role in the fade properties and humid fastness of ink-jet produced printed images. Thus, for a given ink, the degree of fade and water fastness can be dependent on the chemistry of the media surface. This is especially true in the case of images printed with dye-based ink-jet ink compositions. As a result, many ink-jet inks can be made to perform better when an appropriate media surface is selected.
In order for the ink-jet industry to effectively compete with silver halide photography, it is desirable that ink-jet produced images be color saturated, fade resistant, and water fast. Thus, enhanced permanence of dye-based ink-jet ink produced images is becoming more and more integral to the long-term success of photo-quality ink-jet ink technologies. At this point in time, for instance, according to accelerated tests and “industry standard” failure criteria, photographs typically will last about 13 to 22 years under fluorescent light exposure. The best dye-based ink-jet ink printers produce prints that last for much less time under similar conditions.
A few categories of photographic ink-jet media are currently available, including polymer coated media, clay coated media, and porous particulate coated media. It is the polymer-coated media that provides for the longest lasting ink-jet ink produced images. However, this category of media is generally inferior in dry time and humid fastness relative to porous coated media. On the other hand, image fade resistance and humid fastness of porous coated media is generally lower than that of its polymer coated media counterpart. Therefore, there is a great desire to improve the image permanence of ink-jet ink images printed on porous coated media.